AN  APPARATUS  FOR  THE  MEASURE- 
MENT OF  THE  PARTIAL  VAPOR 
PRESSURES  OF  THE  BINARY 
SYSTEM  AMMONIA- WATER 


ARNOLD  O.  BECKMAN 


THESIS 


FOR  THE 


13KGKEEOFBAGHELOROF  SCIENCE 


IN 


C liEMICAL  ENGINEERING 


c;OLLE(JE  OF  LIBERAL  ARTS  AND  SCIENC^ES 


ITNIVEKSITY  OF  ILLINOIS 


1922 


X 

'X 


.C 

tC 


UNIVERSITY  OF  ILLINOIS 


__A_ugusi._l.Q_-_i923__. 


THIS  IS  TO  CERTIFY  THAT  THE  THESIS  PREPARED  UNDER  MY  SUPERVISION  BY 

_A  r n Q_1  d_  _Qr_v  i_l  1 8.  _ Be  c kman 

ENTITLED  Aipparatus  for  the  Measurement  of  the  Partial 

y_§P_QP_  _ Pil®  s_3u_r  e ?_  _ p_f  _ _t  he_  _ B inp-ry  _ Sx§  t_®  m r_»_ 

IS  APPROVED  BY  ME  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR  THE 
DEGREE  OF  ___BacJae_lo2i_p_f __ScjLence_ 



Instructor  in  Charge 

Approved  : 

head  of  department  of 

* ' t...  J w ■ A- 


Digitized  by  the  Internet  Archive 
in  2016 


https://archive.org/details/apparatusformeasOObeck 


Table  of  Contents. 


I.  Introduction  1 

II.  Historical  3 

III.  Theoretical  5 

Diagram  of  Apparatus  7 

IV.  The  Apparatus  8 

V.  Calibration 13 

VI.  Operation  17 

VII.  Summary  19 

VIII.  Acknowledgments  20 

IX.  Bibliosraphy  21 


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I.  Introduction. 

The  measurement  of  the  total  and  partial  vapor  pressures 
of  aqueous  ammonia  solutions  was  undertaken  primarily  for  the 
purpose  of  obtaining  new  data  for  use  in  connection  with  the 
absorption  system  of  ammonia  refrigeration.  In  developing  the 
thermodynamic  relations  of  the  properties  of  ammonia  solutions 
to  be  used  in  this  work,  it  was  found  that  the  data  available 
was  neither  sufff“iciently  accurate  nor  extensive  enough  in  its 
scope  to  permit  of  satisfactory  mathem*atical  treatment.  There 
was  an  urgent  need  for  accurate  determinations  of  the  vapor 
pressures  of  ammonia  solutions  v/hose  concentrations  ranged 
from  0 to  50  percent  at  temperatures  of  O'^to  120*  C. 

From  a theoretical  standpoint  the  determination  of  the 
partial  pressures  should  prove  very  interesting.  The  anom- 
alous behaviors  of  both  water  and  ammonia  are  demonstrated  in 
many  of  their  properties  and  it  is  reasonable  to  expect  a sim- 
ilar non-conformity  with  the  laws  governing  vapor  pressure. 
From  accurate  measurements  of  the  partial  pressures,  the  dev- 
iation from  Raoult's  and  Henry's  laws  could  be  expressed. 

Since  the  determination  of  the  partial  pressures  involves  a 
measurement  of  the  total  vapor  pressures,  it  v;as  decided  to 
carry  out  both  determinations. 

The  problem  undertaken,  then,  was  one  of  designing  an 
apparatus  which  would  perm-it  the  determination  with  a high 
degree  of  accuracy  of  the  total  and  partial  vapor  pressures 
of  aqueous  ammonia  solutions  of  all  concentrations  over  a 


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temperature  range  of  0°  to  120*^0 , and  a pressure  range  of  app- 
roximately 15  to  800  cm.  of  Hg  (l/5  to  10  atmos , ) , these  limits 
being  those  met  with  in  actual  refrigerating  practise  and  suf- 
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II.  Historical, 


3. 


The  first  determinations  of  the  vapor  pressures  of  aqueous 
ammonia  solutions  which  were  of  any  importance  v/ere  those  obtained 
by  Slms^  in  1861*  He  determined  the  total  vapor  pressures  by  the 
static  method  at  the  tem.peratures  of  0**,  20°  40^  and  100°  C,  He 

employed  only  very  dilute  solutions  in  his  work. 

2 3 4 

Perman  ' * S in  1903,  was  the  first  to  make  measurements 
over  any  considerable  ran^e  of  concentrations,  v/orking  with 
solutions  containing  0 to  22,6  percent  of  amm.onia  at  temperatures 
of  0**  to  60'*C.,  no  pressures  higher  than  535  mm.  of  Hg  being 
measured,  however.  He  used  a dynamic  m.ethod  which  consisted  of 
blowing  air  through  ammonia  solutions  under  certain  condij^tions , 
then  from  the  composition  of  the  resulting  vapor  calculating 
the  partial  vapor  pressures  of  its  constituents.  This  method 
is  not  applicable  to  high  concentrations,  however,  because  the 
ratio  of  the  airmionia  content  to  that  of  the  water  in  the  vapor 
drawn  off  becomes  so  great  that  the  results  are  inaccurate. 

Even  at  the  concentrations  used  by  Perman  the  results  did  not 
check  very  well,  Perman ’s  v;ork,  also,  is  based  upon  several 
assumptions  of  rather  doubtful  validity  (as  the  statement  that 
Raoult’s  law  holds  for  ammonia  solutions)  that  his  results, 
while  seem.ing  to  check  fairly  w'ell  with  themselves,  must,  never- 
theless, be  looked  upon  with  suspicion. 

The  most  recent,  and  to  this  date,  the  most  reliable  data 

5 

is  that  secured  by  Hilde  Mollier  in  1908,  working  in  the  labor- 
atories at  Kdnchen.  Her  report  included  values  of  vapor  press- 


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ures  up  to  700  cm.  of  Hg  ( 9,2  atmos.),  at  temperatures  of  0**  to 
120^  C.,  and  concentrations  of  11.80,  23.39,  33.73,  41,55,  and 
50.31  percent.  The  method  followed  v;as  the  usual  static  method 
in  which  the  pressure  above  the  amjnonia  solution  contained  in 
a closed  vessel  surrounded  by  a constant -temperature  bath  was 
measured  by  an  open  manometer.  From  the  data  siven  in  her  report 
hov/ever,  it  is  seen  that  the  analyses  of  the  ammonia  solutions 
do  not  check  v/ithin  the  desired  degree  of  accuracy.  Moreover, 
her  work  affords  only  the  total  vapor  pressures. 


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III.  Theoretical. 

The  usual  method  of  obtainlne  the  partial  vapor  pressures 
of  any  substance  in  solution  is  to  assume  that  Raoult’s  law  holds 
and  then  to  calculate  the  partial  vapor  pressures  from  the  total 
vapor  pressures  and  the  com-positions  of  the  solutions.  In  this 
case,  however,  since  it  is  desired  to  show  whether  or  not  Raoult’s 
lav/  does  hold  for  aqueoLis  amjnonia  solutions,  the  law  cannot  be 
used  in  the  calculations.  Since,  then,  the  partial  vapor  press- 
ures cannot  be  calculated  from  a knowledge  of  the  composition 
of  the  liquid  phase,  some  method  must  be  devised  whereby  the 
vapor  phase  miay  be  analyzed.  Then,  knowing  the  composition  of 
the  vapor,  the  total  vapor  pi^essure,  and  the  vapor  pressure  of 
water  (from  Landolt-B8rnstein) , the  application  of  Dalton's 
law  will  Give  the  partial  vapor  pressure  of  the  ammonia. 

In  order  to  make  possible  an  accurate  analysis  of  the 
vapor  phase,  it  is  desirable  to  have  a large  quantity  of  the 
vapor  for  analysis.  Consequently,  the  apparatus  should  be 
designed  with  a com.paratively  large  space  for  the  vapor  phase. 

Since  samples  of  both  the  vapor  phase  and  the  liquid  phase 
are  to  be  rem.oved  for  analysis,  some  arrangement  should  be  in- 
corporated whereby  the  com.position  of  each  phase  will  not  change 
while  the  portion  of  the  other  phase  is  being  removed.  This 
could  be  done  by  separating  the  two  phases  after  equilibrium 
has  obtained  and  the  total  vapor  pressure  determined. 

In  order  to  permit  the  use  of  hie:hly  concentrated  solutions 
v;ith  their  accompanying  high  vapor  pressures,  it  seems  advis- 
able to  prepare  the  solutions  v/ithin  the  apparatus  itself.  As 


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coFjnercial  ammonia  can  be  obtained  with  a hieh  degree  of  purity, 
it  could  be  used  for  this  purpose.  As  ordinarily  sold  in  tanks 
it  is  under  a pressure  of  approximately  10  atmospheres  at  room 
temperature,  so  that  the  ammonia  could  be  forced  by  its  ovm 
pressure  into  the  apparatus. 

For  measuring  the  pressures,  the  mercury  manometer  offers 
itself  as  the  best  device.  It  would  be  extrem.ely  difficult  to 
find  pressure  guages  made  of  a material  not  readily  attacked  by 
amm.onia,  and  even  if  such  a device  were  available,  it  v;ould  need 
frequent  calibration.  The  mercury  manometer  is  simple  in  oper- 
ation and  gives  the  absolute  values  directly. 

The  apparatus  must  be  made  of  some  substance  not  readily 
attacked  by  either  ammonia  or  mtercury.  The  two  materials  which 
suggested  themselves  were  glass  and  iron.  A test  was  made  in 
which  pieces  of  glass  and  iron  were  boiled  for  the  same  length 
of  time  in  ammtonia  solution.  It  was  found  that  the  glass  spec- 
imen lost  much  more  in  weight  than  did  the  iron  specimen.  For 
this  reason  the  apparatus  was  made  of  iron.  Iron  has  the  add- 
itional advantage,  also,  of  possessing  a much  higher  tensile 
strength  so  that  the  higher  pressures  could  be  used  with  safety 
in  the  apparatus « 

With  the  foregoing  considerations  in  mind,  the  apparatus 
described  in  the  following  pages  was  designed  and  constructed. 


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IV . The  Apparatus . 

The  ammonia  solution  is  contained  in  the  vessels  A and  A,, 
made  of  2 inch  black  wrought-iron  pipe.  The  upper  container 
A is  22  inches  long  and  has  a capacity  of  942  cc.  The  lov/er 
container  A,  is  16  inches  long  with  a capacity  of  650  cc.  In 
order  to  facilitate  the  attainment  of  equilibrium  within  the 
system,  A.  is  provided  v;ith  a baffle-plate  arrangement  made  by 
twisting  an  iron  rod  of  small  diameter  into  a loose,  irregular 
bundle.  The  t?/o  pipes  are  closed  by  caps  at  each  end,  the  two 
adjoining  ends  being  connected  through  the  1 inch  valve  X.  Into 
the  cap  at  the  bottom  of  A,  is  screwed  an  l/8  inch  pipe  which 
extends  over  to  the  mercury  reservoir  and  manometer.  In  assem.b- 
ling  the  apparatus  it  was  found  necessary  to  put  a thin  mixture 
of  glycerine -litharge  cement  on  the  pipe  threads  at  all  of  the 
joints  for  only  in  this  manner  could  a vacuum-tight  joint  be 
obtained. 

Since  it  is  necessary  to  have  som^e  method  of  keeping  the 
meniscus  of  the  merciiry  column  v/ithin  the  apparatus  at  a con- 
stant level,  some  device  had  to  be  installed  for  this  purpose. 

A glass  tube  v/as  inserted  at  B so  that  the  meniscus  could  be 
easily  seen  and  kept  at  a certain  mark.  A great  deal  of  dif- 
ficulty was  experienced  in  finding  a suitable  means  of  sealing 
the  glass  tube  to  the  iron  pipe  so  that  the  joint  v/ould  be  im- 
pervious to  ammonia  and  mercury,  and  at  the  same  time,  be  vac- 
uum-tight. The  method  v/hich  was  finally  successful  was  this: 

The  l/s  inch  pipe  on  either  side  of  the  glass  tube  was 


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fitted  v/ith  a 3/8  inch  bushing  on  which  v/as  screv/ed  a s/s  inch 
coupling.  The  ^lass  tune  was  then  selected  of  such  a size  that 
it  fitted  easily  into  the  couplings.  The  space  betv;een  the 
glass  tube  and  the  couplings  was  filled  with  glycerine-litharge 
cement.  After  the  cement  had  hardened,  it  v;as  covered  with  a 
layer  of  deKhot insky  cement.  This  last  covering  of  the  deKho- 
tinsky  cement  vi/as  found  to  be  necessary  as  the  glycerine-lith- 
arge cement  is  slightly  porous  and  allov;ed  air  to  diffuse  slowly 
into  the  vessels  A and  A.  vfnen  the  apparatus  was  evacuated.  The 
layer  of  deKhotinsky  cement  remedied  this  trouble  entirely. 

C is  a black-iron  union  inserted  for  the  purpose  of  simp- 
lifying the  assembling  of  the  apparatus.  It  is  located  about 
80  cm.  belovj  the  meniscus  line  at  B so  that  at  all  times  there 
is  pressure  within  the  union.  This  was  found  necessary  as  the 
union  leaked  slightly  under  hieh  vacuum.  Under  pressure,  how- 
ever, the  union  did  not  leak,  the  mercury  inside  evidently 
providing  a sufficient  seal. 

D is  a reservoir  for  the  mercury  made  of  2 inch  iron  pipe. 

A guage-tube  at  the  side  registers  the  level  of  the  mercury 
within  the  tube.  At  the  top  of  the  tube  a needle-valve  Y is 
placed.  On  top  of  Y is  a two-way  stopcock.  One  side  of  the 
stopcock  is  connected  to  the  compressed-air  line  and  the  other 
to  the  vacuum  line  in  the  laboratory.  Then,  by  turning  the 
glass  stopcock,  either  pressure  or  vacuum  ii  put  upon  the  valve 
Y.  Since  Y is  a needle-valve,  this  pressure  or  vacuum  can  be 
very  gradually  applied  to  the  mercury 'within  the  tube,  thus 
allowing  a very  accurate  adjustment  of  the  meniscus  level,  A 


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V/-TT  -A. 


10 


plug  in  the  tee  at  the  bottom  of  the  guage-tube  affords  a means 
of  filling  the  tube  with  mercury  and  a similar  plug  at  the 
bottom  permits  the  tube  to  be  emptied. 

The  manometer  E is  simply  a straight  glass  tube  inserted 
into  a coupling  and  sealed  as  in  the  case  of  the  glass  tube  at 
B,  In  this  case,  hov/ever,  the  tube  is  sealed  in  with  deEho- 
tinsky  cement  alone  as  the  ammonia  does  not  come  in  contact 
with  this  part  of  the  apparatus.  There  is  the  added  advantage, 
too,  that  the  manometer  tube  can  be  removed  at  any  time  by 
simply  heating  the  joint.  This  is  helpful  v/hen  the  open  man- 
ometer is  replaced  by  a closed  manometer  for  use  at  higher  press- 
ures. The  height  of  the  meniscus  may  be  read  from  the  scale 
shown  or  by  means  of  a cathe tome ter. 

Into  the  vessel  A,  a -g-  inch  pipe  is  soldered  v/hich  termin- 
ates in  the  valve  F on  the  outside  of  the  thermostat  tank. 

This  valve  is  for  the  purpose  of  withdrawing  the  sample  of  the 
liquid  phase  from  A,  as  will  be  explained  later.  At  the  top 
of  A,  pipe  connections  are  so  arranged  that  by  means  of  the 
valve  W amiionia  gs  s from  the  tank  I may  be  introduced.  The 
valve  V has  several  functions.  It  allov/s  the  vessels  A and  A. 
to  be  evacuated  by  connecting  the  vacuum  line  with  the  system 
through  the  connection  at  F.  By  connecting  through  the  collect- 
ing vessels  H a sample  of  the  vapor  may  be  brought  off  for  an- 
alysis. By  connecting  with  G water  may  be  introduced  for  the 
purpose  of  making  the  ammonia  solutions. 

For  m.aking  these  connections,  Y is  connected  to  the  part 
of  a union  containing  the  female  thread.  Then  parts  of  exactly 
similar  unions  containing  the  male  thread  are  attached  to  G,H, 


*■*  . . . ^ 'j.  ^ . * •”.;  ...  ill/  ' '■'  ■ . „ ' 


V 5»<‘<''  * 2*./li5f  rQ  r.O 

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tM 


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.itLi 


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itU  , V'  ;.,  .1.1-.  -2.  .\jM  , 

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"*  '^  ' •'  '"  V''.  ^ '^‘  ■ , ’’'  r /'  ^ s'  ' .^Wil  IM 

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11. 

etc.,  so  that  connection  may  be  made  with  any  one  by  screwing 
the  union  together.  G is  a glass  funnel  sealed  into  the  union 
with  deKhot insky  cement.  H consists  of  two  collecting  flasks, 

H.  containing  standard  dilute  sulfuric  acid  and  H. . containing 
concentrated  sulfuric  acid.  The  latter  vessel  is  connected 
through  a glass  stopcock  to  the  vacuum  line  J. 

The  vacuum  line  J is  made  of  l/8  inch  pipe  v^ith  glass  stop- 
cocks sealed  in  as  shown  in  the  diagram.  The  stopcocks  are 
sealed  in  with  deKhotinsky  cement  in  a manner  similar  to  that  of 
sealing  in  the  manometer  tube.  The  upper  stopcock  is  for  the 
purpose  of  shutting  the  vacuijim  piimp  P from  the  line.  The  next 
stopcock  allov/s  the  vacuum  to  be  applied  to  the  sampling  vess- 
els, The  third  stopcock,  v^hen  connected  to  F by  means  of  press- 
ure tubing, allows  the  tv/o  vessels  A and  A.  to  be  evacuated. 

At  the  bottom  of  J another  stopcock  is  placed  to  be  used  in 
drav/ing  off  the  samples  of  the  liquid  phase,  Imm.ediately 
above  this  another  stopcock  is  placed  so  that  the  vacuum,  within 
the  line  may  be  released  at  any  time.  The  manometer  J registers 
the  degree  of  vacuum  v/ithin  the  line. 

The  vessels  A and  A.  are  surrounded  by  the  thermostat 
tanks  T and  T..  The  thermostat  tanks  are  made  of  sheet  iron 
surrounded  by  a thick  layer  of  wool  to  insulate  the  tanks  from 
the  surrounding  atmosphere.  The  stirrers  operated  from  the 
line  shaft  by  the  motor  M,  are  of  sufficient  size  to  give  ad- 
equate stirring.  The  temperature  is  regulated  by  the  U-shaped 
mercury  regij.lators  shov/n.  These  operate  in  the  usual  v/a:/-, 
the  low-voltage  current  being  furnished  by  the  dry  cells  L, 

The  r,esistance  N regulates  the  current  which  flov;s  through  the 


JJ 


f 


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tl 


I'.'' 


4-*j. 


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a Z 0 


1^' 


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*« 


'IT  J 


12. 

relay  R,  On  the  other  side  of  the  relay,  the  110  volt  current 
is  connected  through  the  relay  to  the  heating  lamps  at  K. 

In  addition  to  this  regulation,  there  are  coils  (not  shovm 
in  the  diagram)  within  the  tank  through  v/hich  cold  water  m.ay 
be  circulated.  The  liquid  in  the  t'mks  is  vmter  for  the  m.easure 
ments  at  0 C . and  oil  for  the  other  temperatures. 

The  valves  V,  V7,  F., , and  Y are  made  especially  for  use 
with  ammonia  solutions.  They  are  built  by  York  and  Company, 
and  are  of  the  so-called  expansion  type.  The  needle  seats 
both  v^hen  the  valve  is  open  and  when  it  is  closed.  This  el- 
iminates the  leaking  around  the  valve  stem  v/hich  Vi/ould  other- 
wise occur,  and  permits  a high  degree  of  vacuum,  or  a high 
pressure,  to  be  maintained  indefinitely.  Since  the  valves  are 
of  the  needle  type,  they  permit  a very  gradual  release  of  the 
pressure.  The  valve  X is  of  the  globs  type  and  also  seats 
either  open  or  closed. 


^ -^-  ;*irft4wm  (I'lOv.  Q/l  .^'^f»rVx| 

ifl  ‘ : ,,  flB  ■*-  • .-,.  I'S 


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rnwrte  ioia,  afj.-3  -x..  fi-niy  ./roid^n^B., 


ltd?-  ns.•a^lt«»^<.(»  !»?..';»  ■<*<««  (dSjaiit*«4#;.^  ;; 

-ftaij-u,*  ,114  -((rt'Tfcii*  .t  «aitidi  |' 

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■'4 

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<Ml  r It  SiiH/  a#4*v  r«*.  « i ^ ^ t *^.>'’  . * .. 


13. 


V . Calibration. 

In  using  the  apparatus,  the  first  thinp  to  be  carried  out 
is  the  calibration  of  the  manometer.  A m.ark  0 is  drav/n  upon 
the  scale  at  B as  the  fixed  position  of  the  meniscus.  Then, 
with  the  vessels  A and  A.  open  to  the  atmosphere,  the  level  0 
should  be  marked  upon  the  manometer  scale.  Then,  in  taking 
readings,  the  position  of  the  manometer  meniscus  above  or  belov/ 
that  mark  will  be  a m.easure  of  pressure  above  or  belov;  atmos- 
pheric v/hich  exists  within  the  apparatus. 

The  pressure  which  is  v;anted  is  that  at  the  surface  of 
the  livmid  phase.  Therefor  the  pressure  read  upon  the  manometer 
must  be  corrected  for  the  pressure  due  to  the  liquid  within  A, 


where 


Pv 

Pi 


the  vapor  pressiire  of  the  solution. 

the  total  pressure  as  read  upon  the  manometer. 

the  pressure  due  to  the  column  of  liquid. 


P-t  can  be  read  directly  from  the  manometer;  P^  is  the  quantity 
to  be  determined  experimentally;  P]_  must  be  calculated. 

The  pressure  at  the  bottom  of  the  column  of  ammonia  sol- 
ution is  equal  to  the  v;eight  of  the  solution  divided  by  the 
cross-section  area  of  the  tube.  The  area  of  the  cross-section 
of  the  2 inch  pipe  of  the  vessel  A.  may  be  found  by  adding  a 
known  volume  of  water  to  the  vessel  and  measuring  the  heiftht 


i 


\ 


, 8jL  0 


r 


ffiofn 


J..I 


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y~i 
t‘'  ' :^Uf 


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piTw  S 


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' S.''.',:  V.u  ■ 


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t .J  iV  n:*  'io 


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'■•.V 


14. 


of  the  resulting  colurnn  of  liquid,  (This  must,  of  course,  be 
done  before  the  apparatus  is  assembled.) 

Then 

where 

V “ volume  of  the  water  added. 

H - height  of  resulting  column  of  v/ater. 

A = cross-section  area  of  the  pipe. 

The  calculation  of  the  v;eight  of  the  solution  is  simplified  if 
it  is  considered  as  being  made  up  of  two  parts:  airmionia,  v/hose 
weight  is  a variable  quantity  depending  upon  the  concentration 
of  the  solution,  and  water,  which  has  a constant  weight  in  all 
determinations.  This  last  statement  is  true  providing  the 
solutions  are  made  by  adding  ammonia  to  the  same  weight  of 
water  in  each  determination,  and  that  is  the  method  of  procedure 
v/hich  will  be  followed  in  using  the  apparatus.  The  pressure 
due  to  the  water  then,  is  a constant  correction. 


W 


H2O  . p 
A 


HgO 


VJhen 


W jjgo  ” weight  of  the  v/ater  added  ( 500  grams  ), 

A : cross-section  area  of  the  tube. 

P Q = pressure  due  to  the  water  in  the  solution. 

^ ( srams-weip-ht ) . 

There  remains  the  problem  of  finding  the  pressure  due  to  the 
ammonia  in  the  solution. 


"iy*  ■ • '■  >-^: 


•> 


'<Vi' 

,4' 

' n-v 


» ,^V*  , ^ V>“  ' 

'‘...a  ■ ' V.,*  < ' '‘4*5*' 


,‘>r'fi 


X 


*S: 

m 


' jlij 

■X-  ' if  ‘ 

=f.v  # W’ 

•V  - . ‘ I’  • * 


.y'.  %ivj><  ; ufQ,#  r-lif  V-  , 

f'*  r^  -*  ’ " ‘ ' ■ '• 

, .•■'.N'fc./r. 7 /T*  • •>rfi  r^r.'/'jo'  j^%-: i '] 

p^^,\it!:  /n*-£^«  4 6i.M"  ,‘r->  ,im 


♦ lO  p*Ali.}(  a*r/rn  ujj  •^ii^;9P'ir?‘  ^i^fas 


“ ',-j 


•'»U'  ''^1 


I ‘J_-.;,.|««'tiI  lo  fcc..i-»>Jr:.|K;#  =i  S<>t^.  -MiW'  ^ fit  H^t, 

•■■*  ^WS*«-ni  etT  . enlist  .n>»  >:i  ji(,<l  ‘ ti  ni'- ,«<(  Xil'i  ' 

/ ■■"  * ' ~ •';  j)  ' '■  ' ' 

V4'  'jr^r-  ^'Vj^n;-a._i  "i:>  ^yi ; 0J^‘  /i* 

• — • — 


'H'-  - 


,v  . V -ts 


'•  ■* 
A 


• I 


XiStSS' 


r'-.v^-s 


- >' 


-•rtw  ’'•■"  lb  b.:>^-'*‘.- 


eJ 


5k,  T^- 


’ a 


t 


# i * i '• " - " T"  « y~ 

*h,^l\  t ..  >ip  03T  ©^',  Sk'j.f»«8 0‘t(^ 

■•  o-  - V.-.  !■-?.,«».•.  ssj.:^j| 


-•it,; 


'<  ■ 

.< 


15. 

trom  the  analysis  of  the  liquid  phase,  the  weieht  of  the 
ammonia  in  the  solution  may  be  found. 

Then 

A “ 

This  quantity  must  be  determined  for  each  experiment. 

It  will  be  noticed  that  the  pressure  due  to  the  solution 
was  calculated  on  the  assumption  that  all  of  the  solution  was 
in  A,,  a tube  of  constant  cross-section  area.  There  is  an 
additional  pressure  due  to  the  liquid  contained  in  the  l/s  inch 
pipe  and  the  glass  tube  leading  from  A,  to  the  mercury  ijieniscus 
at  B.  The  volume  of  this  amount  of  the  solution  is  so  small 
that  it  need  not  be  subtracted  from  the  original  500  cc.  of 
the  water, (all  of  which  v; as  assumed  to  be  in  A.)  on  account 
of  the  large  cross-section  area  of  A,.  In  the  l/s  inch  pipe 
and  the  glass  tube,  hov;ever,  the  cross-section  area  is  so  small 
that  the  resulting  height  of  this  small  volume  must  be  considered. 
This  additional  pressure  may  be  found  by  measijiring  the  distance 
from  the  meniscus  level  at  0 to  the  vessel  A,  This  height, 
multiplied  by  the  density  of  the  solution  ( from.  Landolt -Born- 
stein)  for  the  particular  concentration  ¥/ill  give  the  last 
correction  to  be  made, 

- Px 

v^here 

H = the  height  from  0 to  A, 

D = the  density  of  the  solution, 

Px  z pressure  correction  for  this  height  of  solution. 


5 Tn  'fr V* 


#V 


F 


1 \ 

■ 'i' 

' ■?,  V '*,'  _ , 

. • ‘V  '.1^, 

J f :3 

^'C<  vttr  - 


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it 

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X.«. 


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16 


Then 


Pi 


13.595 


where 

P-,  - the  pressure  due  to  the  total  weight  of  the  solution. 
( in  cm.  of  Hg.) 


t 


17 


VI.  Operation . 

For  the  0*  C.  readings  fill  the  tanks  with  crushed  ice. 

For  the  higher  temperatures  fill  the  tanks  v/ith  oil.  Set  the 
thermostat  regulators  to  give  the  desired  temperatures. 

Open  X,  connect  F to  the  vacuum  line  J and  evacuate  A and 
A..  Close  V,  attach  G and  add  500  cc.  of  water,  closing  V 
quickly  as  soon  as  all  of  the  v/ater  is  introduced  into  A to 
prevent  the  introduction  of  much  air. 

Open  W,  admitting  the  ammonia  gas  until  the  solution  is 
of  the  desired  strength.  This  can  he  told  roup:hly  from  the 
reading  of  the  manometer.  Stir  the  mixture  somewhat  by  lowering 
and  raising  the  mercury  in  A,.  Close  X and  evacuate  A.  Open 
X for  a minute  and  evacuate  A.  again.  This  process  eliminates 
any  air  which  may  be  contained  v/ithin  the  system.  Close  V and 
stir  until  equilibrium!  is  obtained.  This  can  be  judged  from 
the  readings  of  the  manometer.  VJhen  there  is  no  difference 
betv/een  successive  readings  taken  a few  minutes  apart,  the 
system,  is  in  equilibrium. 

V/hile  the  system  is  coming  to  equilibrium,  H ( and  a 
similar  collecting  device  for  the  liquid  phase)  should  be 
weighed.  A.fter  the  equilibrium  has  been  obtained,  read  the 
manom.eter  E,  close  X and  draw  off  a sample  of  the  vapor  phase 
through  H.  and  H.  . . Dravj  off  a samiple  of  the  liquid  phase 
throuc-h  F.  . In  drav/ing  off  the  sample  be  sure  to  get  the  press- 
ure on  the  outer  end  of  the  sampling  train  lower  than  that 
v/ithin  the  system,  otherv/ise  the  sulfuric  acid  v/ill  be  drav/n 


■Bi 


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Ks  ■ . MJ  -•>>*  ei 

^ :.  • V « 4?ofr«rai»  qiKid'^  >> 

.no  t y 'oaojO  \vA 

• 0.?  '‘u:  bc'.up.t’r^-.M  t«  rir;  b;»  , nopr  «i>  'xSit6lvp 


I. 

V -4A't:0' 


. 'IB  ,i-M?»  1,  noi  ;94-w'*tof  ‘*yf^  \.rt4wW 


■ Aiwa  •-<  -.,1. 

piwrr-i  - - •*  M»nr,j.B-'^!P.,vfx,irt  -.f‘  *«  .*.<,(x*m. 

• ft 


£**'  • ''T^*  w*'  •* 


t' 

k 


0^  V 9,clJ  ■..■■:  .,,,;,  BJ.-, «!«•....  ed  v.,  i^dlV*.  lliiM- 

rj.fe  b/j«e  •-f.*,I«di')Bi  «AL^«ilud» 


' 'l*t. 

- ii 


' 


J ■'  .» 


i' 


i,i  O'Xriii/  TAtfW'  ®rt^  <W§^' 

ff>r*.rxi-s-Y»4’  A-  ;o*:fiijf  rt0mi&d 


: 'S-  ■ tfl.  '‘‘K 

^1  ^ Mojvnb  .««<iir6'#(t6a.'^^t^i^'  ‘■ij 

u«id  k'H  'i*rt 

&imr  «d#  . la  i,.X<E-«,  nc  fl(.i  . V 


•1^.^  .'ifs,  -3  Vj-zix  .«is  vto  s.iit.fe.ia''ja-  ..^  iJiSodiftfix ' 


-.■‘jf'-.'*'*^  fuj'x  .s-oSraf  :,.,i,...  yt,! ' <»{«  «.  Jo' tn»  -;  ■.sro  arfjf.vlA  sp' 
^-.1/,  4d  XXJ  .r  d|»,,  aartrjjr,,.  ,.  :•,;/ .;  ■ 


into  the  apparatus.  For  the  low  concentrations  and  temperatures 
it  v\Till  be  necessary  to  connect  the  collecting  vessels  to  the 
vacuum  line  J,  but  at  the  higher  concentrations  and  temperatures 
the  pressure  within  the  apparatus  will  be  higher  than  atmos- 
pheric so  that  this  procedure  will  not  be  necessary. 

Weigh  the  sampling  trains  again,  then  titrate  the  excess 
acid  with  n/10  NaOH.  This  v/ill  give  the  -weight  of  the  ammonia 
in  the  vapor  and  liquid  phases.  The  weight  of  the  vmter  in 
each  case  is  found  by  subtracting  the  weight  of  the  ammonia 
from  the  total  increase  in  weight  of  the  collecting  vessels. 

The  weight  of  the  ammonia  is  then  used  to  determine  the 
pressure  corrections  as  described  -ujider  Calibration, 


The  treatment  of  the  results  is  beyond  the  scope  of  this 
paper.  Work  is  in  progress  on  the  actual  measurement  of  the 
total  and  partial  vapor  pressures  and  the  data  obtained  will 
be  submitted  at  a later  date. 


• .VT'‘  ' 


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Mr!  rj  J’  Ki  f.n  fi-v  ai^t  "il#  40^rio  . 9.  vTfl*Wo><T'  -jd  i-.*  J1  }i‘ 


Ortif  Jfs  $i*t(  *lr  "e«±x,'pu/j;/drtY  i 

r.-  . ><1A,  »W: 

4 ■■  .1  ' • ♦=  ' ’ w 

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■-ft«  to-  ».-7-->K5ti (!»»»■  W4-  dti  BBO-sso^qinl  i-jo^  .‘ia^<ta' 


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19. 

VII,  Sumnar:;- , 

1.  An  apparatLis  has  been  designed  and  constructed  which 
will  permit  measurements  to  be  made  vifith  a hifrh  dej2:ree  of 
accuracy  of  the  total  and  partial  vapor  pressures  of  aqueous 
ammonia  solutions, 

2,  The  calibration  and  the  mode  of  operation  have  been 
described  in  detail, 

o.  Work  is  in  progress  on  the  measurement  of  the  total  and 
partial  vapor  pressures  of  aqueous  ammonia  solutions. 

I 


t 


. 8 rf 1 1 ^ jjf^  0 inokrfjS 


T,! 

i 


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\n: 


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-Ti 


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f:^  '°IS3;  ' 4:4  ' ' 

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20. 

VIII.  Acknowledp;inents . 

The  apparatus  descrihed  in  this  paper  was  designed  and 
constructed  by  the  joint  efforts  of  llr,  Thomas  A.  Viilson  and 
the  author . 

The  author  wishes  to  express  his  sincere  gratitude  to  those 
who  have  helped  him  in  his  work  on  this  problem.  Dr.  G.  Diet- 
richson,  under  whose  direction  the  w^ork  was  carried  out,  has 
maintained  an  untiring  interest  in  the  problem  and  has  given 
many  thoughtful  criticisms  and  suggestions.  Dr.  Rodebush 

and  T.E.  Phipps  have  offered  much  valuable  advice  which  greatly 
simplified  the  construction  of  the  apparatus. 


r-t; 


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I 


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Ky¥  *■  '•>•  * i' 


\ 'V  ■ ■ 


' ^ '^.^f- \'  -1'  " 


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V .s '., V ■ ' -'  ”'  im 

':'.<*-  .£■  " ' ' . ■■  i'/'"' •■TJ.sy  i 5 


ifr.» 


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I ‘0»S  <*• 


ls.‘  ‘ill. 


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I'-  : /.  ■ ■.■  '•'■  ^ h . ,^, 


'-fe  ^ V • • ^4*r.’ *i ’ vi  » t ^ 

.;  \ *’  .••'  ■■'  ''  5 '1  ' ... 


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^ s t ’ 


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<•  »;^. 


Its 


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ts. 


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>WJa  .^.ivfe , . i,  .-.-  VI, 


.A;;- 


l?:raa»JL;=gagK3S:’Xkij^ 


21. 


IX . Blbliop-raphy , 

(1.)  Ann.  d. , Chem.  u,  Pharm.  118,  1861, 

(2.)  Journal  of  the  Chemical  Society,  22.*  (1901),  718. 

(3.)  Ibid.  83,(1903),  1186. 

(4.)  Proceedings  of  the  Royal  Society,  22*  (1904)  72. 

(5.)  Zeitschrift  d.  Vereines  deutscher  Ingenieure,  52,  (1908), 1315. 


